Polyvinyl alcohol flexible production method and system based on multi-reactor group collaborative control

Abstract

The present application provides a polyvinyl alcohol flexible production method and system based on multi-kettle group collaborative control, relates to the technical field of polymer chemical industry, and the method comprises the following steps: real-time estimation of the dynamic deviation of the actual monomer concentration in the first polymerization kettle; according to the dynamic deviation, the basic residence time of the post-polymerization kettle is fed forward compensated before reflux disturbance to obtain the compensated residence time, and the liquid level control threshold of the post-polymerization kettle is determined; the addition temperature of the lye is matched with the temperature rise to obtain the addition temperature execution value of the lye; the instantaneous heat release rate of the polyvinyl acetate intermediate during the alcoholysis reaction is real-time calculated; the heat release response type dynamic adjustment is performed on the belt running speed of the wide belt alcoholysis machine to obtain the belt speed execution value; according to the lye addition temperature execution value and the belt speed execution value, the wide belt alcoholysis is adjusted to obtain the polyvinyl alcohol product; and the present application can improve the efficiency of the polyvinyl alcohol flexible production based on multi-kettle group collaborative control.

Description

Technical Field

[0001] This invention relates to the field of polymer chemical technology, and in particular to a flexible production method and system for polyvinyl alcohol based on multi-reactor group collaborative control. Background Technology

[0002] Polyvinyl alcohol (PVA) is mainly produced through solution polymerization of vinyl acetate to obtain a polyvinyl acetate intermediate, followed by alcoholysis using a belt-driven alcoholysis machine. This is a typical multi-reactor tandem polymerization-continuous alcoholysis process. The multiple reactor units determine the degree of polymerization of the polyvinyl acetate intermediate, while the wide-belt-driven alcoholysis machine is responsible for completing the saponification and alcoholysis reactions of the intermediate, ultimately determining the degree of alcoholysis and the quality of the finished PVA product. During production, reflux disturbances in the first polymerization reactor, fluctuations in monomer concentration within the reactor, and changes in the exothermic reaction in the alcoholysis section are key control points affecting product quality and production stability. Flexible multi-product switching production places high demands on the ability to coordinate and control the entire process.

[0003] Most existing polyvinyl alcohol (PVA) production processes employ fixed-parameter modes for multi-reactor polymerization and belt-driven alcoholysis operations. They lack a feedforward compensation mechanism to address dynamic deviations in monomer concentration caused by reflux disturbances in the first polymerization reactor. The residence time and liquid level thresholds in subsequent polymerization reactors cannot be dynamically adjusted according to the actual state of the monomers within the reactor. Simultaneously, the alcoholysis section relies solely on preset alkali temperatures and fixed belt speeds, failing to capture real-time exothermic changes in the alcoholysis reaction for responsive, coordinated adjustments. The polymerization and alcoholysis processes are independent of each other, lacking collaborative adjustment mechanisms. When flexible production of multiple product lines is implemented or reflux disturbances occur, fluctuations in intermediate quality are easily transmitted downstream, causing drift in the degree of polymerization and degree of alcoholysis of the finished PVA product, resulting in poor product consistency and insufficient production tolerance. Therefore, improving the stability and efficiency of flexible PVA production under multi-reactor coupling has become an urgent problem to be solved. Summary of the Invention

[0004] This invention provides a flexible production method and system for polyvinyl alcohol based on multi-reactor group collaborative control, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides a flexible polyvinyl alcohol production method based on multi-reactor group collaborative control, comprising:

[0006] S01. Real-time acquisition of vinyl acetate and methanol content in the reflux liquid at the outlet of the first polymerization reactor, and based on the feed composition ratio of the target polyvinyl alcohol variety, the instantaneous deviation is obtained by comparing the actual composition of the reflux liquid with the feed composition. Material balance and concentration conversion are performed by combining the feed flow rate, reflux liquid flow rate and material volume in the reactor. After assigning the polarity of the deviation direction, the dynamic deviation of the actual monomer concentration in the first polymerization reactor is estimated in real time.

[0007] S02. Based on the dynamic deviation, perform reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor to obtain the compensated residence time. Based on the compensated residence time, determine the liquid level control threshold of the post-polymerization reactor.

[0008] S03. After introducing vinyl acetate monomer, methanol solvent and initiator into the first polymerization reactor and the second polymerization reactor, the alkali addition temperature is adjusted in reverse compensation based on the difference between the polyvinyl acetate intermediate feed temperature and the alkali solution reference temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. The alkali addition temperature is matched according to the fluctuation of the polyvinyl acetate intermediate feed temperature to obtain the alkali addition temperature execution value.

[0009] S04. Based on the temperature difference of the belt temperature data in the wide belt alcoholysis machine, calculate in real time the instantaneous exothermic rate of the polyvinyl acetate intermediate during the alcoholysis reaction.

[0010] S05. Based on the instantaneous heat release rate, determine the belt speed adjustment direction and adjustment amplitude based on the change in the instantaneous heat release rate, and introduce the rate change at the previous moment to dampen the adjustment amplitude, and perform exothermic response dynamic adjustment on the belt running speed of the wide belt alcoholysis machine to obtain the belt speed execution value.

[0011] S06. Based on the alkaline solution addition temperature and the belt speed, the wide belt alcoholysis is coordinated and adjusted, with the alkaline solution temperature matching the initial activation conditions of alcoholysis and the belt speed matching the reaction exothermic and residence time as the core basis, to obtain polyvinyl alcohol products.

[0012] In a preferred embodiment, the vinyl acetate and methanol contents of the reflux liquid at the outlet of the first polymerization reactor are collected in real time. Based on the feed composition ratio of the target polyvinyl alcohol variety, the instantaneous deviation is obtained by comparing the actual composition of the reflux liquid with the feed composition. Material balance and concentration conversion are performed by combining the feed flow rate, reflux liquid flow rate, and material volume in the reactor. After assigning a polarity to the deviation direction, the dynamic deviation of the actual monomer concentration in the first polymerization reactor is estimated in real time, including:

[0013] Obtain the degree of polymerization and degree of alcoholysis index of the target polyvinyl alcohol variety, and based on the degree of polymerization index, determine the composition ratio of the first batch feed and the basic residence time of the subsequent batches.

[0014] Based on the stated degree of alcoholysis index, the reference temperature of the alkaline solution and the reference speed of the belt in the alcoholysis section are determined.

[0015] At the outlet of the reflux condenser in the first polymerization reactor, the vinyl acetate and methanol content of the reflux liquid were continuously and in real time collected.

[0016] The instantaneous deviation is obtained by comparing the actual composition ratio of the vinyl acetate content and the methanol content with the composition ratio of the first batch feed.

[0017] Based on the real-time monitoring values ​​of the feed flow rate and the reflux flow rate of the first polymerization reactor, the instantaneous deviation is converted into a material difference to obtain the change in the total amount of vinyl acetate monomer.

[0018] Based on the real-time monitoring value of the material volume in the first polymerization reactor, the change value of the total amount of vinyl acetate monomer is converted into concentration to obtain the actual deviation of the total amount of vinyl acetate monomer.

[0019] The concentration deviation direction of the instantaneous deviation is used as a positive or negative polarity indicator, and the actual deviation amplitude is assigned a positive or negative sign to obtain the dynamic deviation.

[0020] In a preferred embodiment, the step of performing reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor based on the dynamic deviation to obtain the compensated residence time includes:

[0021] The deviation magnitude of the dynamic deviation is quantified and extracted to obtain the deviation value of the dynamic deviation;

[0022] When the deviation polarity of the dynamic deviation indicates that the monomer concentration in the first polymerization reactor is lower than the target value, the direction of adjusting the residence time in the subsequent polymerization reactor is determined as the extension direction.

[0023] When the deviation from polarity indicates that the monomer concentration in the first polymerization reactor is higher than the target value, the direction of adjusting the residence time in the subsequent polymerization reactor is determined to be the shortening direction.

[0024] The product of the deviation value and the residence time of the post-reactor foundation is used as the compensation increment;

[0025] The residence time of the post-reactor base is accumulated with the compensation increment over time to obtain the residence time after compensation.

[0026] In a preferred embodiment, determining the liquid level control threshold of the post-polymerization reactor based on the compensated residence time includes:

[0027] The initial liquid level control threshold and the basic residence time of the post-polymerization reactor are retrieved.

[0028] The compensated dwell time is compared with the basic dwell time to obtain the dwell time deviation ratio.

[0029] When the duration deviation ratio indicates that the compensated dwell time is greater than the basic dwell time, the initial liquid level control threshold is adjusted upward.

[0030] When the duration deviation ratio indicates that the compensated residence time is less than the basic residence time, the initial liquid level control threshold is adjusted downward to obtain the liquid level control threshold of the post-polymerization reactor.

[0031] In a preferred embodiment, after introducing vinyl acetate monomer, methanol solvent, and initiator into the first polymerization reactor and the second polymerization reactor, the alkali addition temperature is adjusted in reverse compensation based on the difference between the polyvinyl acetate intermediate feed temperature and the alkali solution reference temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. The alkali addition temperature is matched to the fluctuation of the polyvinyl acetate intermediate feed temperature to obtain the executed alkali addition temperature value, including:

[0032] Based on the aforementioned first batch feed composition ratio, vinyl acetate monomer, methanol solvent and initiator are introduced into the first polymerization reactor, and the first batch of polyvinyl acetate intermediate is obtained at the discharge port of the first polymerization reactor;

[0033] Based on the liquid level control threshold, the first batch of polyvinyl acetate intermediate is introduced into the subsequent polymerization reactor, and the polyvinyl acetate intermediate is obtained at the outlet of the subsequent polymerization reactor.

[0034] The feed temperature of the polyvinyl acetate intermediate is sensed in real time to obtain the feed temperature value of the polyvinyl acetate intermediate;

[0035] Retrieve the reference temperature value of the alkaline solution corresponding to the target polyvinyl alcohol variety;

[0036] The feed temperature reading is compared with the alkali reference temperature value in real time to obtain the temperature deviation of the feed temperature reading relative to the alkali reference temperature value.

[0037] When the temperature deviation indicates that the feed temperature is higher than the alkali reference temperature, the current addition temperature of the alkali is adjusted downward; when the temperature deviation indicates that the feed temperature is lower than the alkali reference temperature, the current addition temperature of the alkali is adjusted upward, thus obtaining the adjusted temperature value of the alkali.

[0038] The magnitude of the temperature deviation is used as the basis for correcting the adjusted temperature value. The larger the magnitude, the greater the correction to the adjusted temperature value, thus obtaining the execution value for the addition temperature of the alkali solution.

[0039] In a preferred embodiment, the step of calculating the instantaneous exothermic rate of the polyvinyl acetate intermediate during the alcoholysis reaction based on the temperature difference value of the belt temperature data in the wide-belt alcoholysis machine includes:

[0040] The temperature difference between adjacent temperature measuring points of the wide belt alcoholysis machine is retrieved, as well as the fixed interval between adjacent temperature measuring points and the current belt running speed of the wide belt alcoholysis machine.

[0041] Based on the fixed interval distance and the current belt running speed, the speed-distance conversion of the polyvinyl acetate intermediate is performed to obtain the travel time of the polyvinyl acetate intermediate;

[0042] The fixed interval distance is timed and merged according to the current belt running speed to obtain the travel time of the polyvinyl acetate intermediate.

[0043] Using the travel time as a time allocation scale, the temperature difference is evenly distributed to each time unit covered by the travel time to obtain the instantaneous temperature rise rate of the polyvinyl acetate intermediate within a unit travel time.

[0044] By combining the mass of material passing through the belt per unit time with the specific heat capacity of the material at constant pressure, the instantaneous temperature rise rate is converted into the instantaneous exothermic rate of the alcoholysis reaction.

[0045] In a preferred embodiment, the step of determining the belt speed adjustment direction and adjustment amplitude based on the instantaneous heat release rate and the change in the instantaneous heat release rate, and introducing the rate change at a previous moment to dampen the adjustment amplitude, thereby dynamically adjusting the belt speed of the wide-belt alcoholysis machine in an exothermic response manner to obtain the belt speed execution value, includes:

[0046] The instantaneous heat release rate is continuously differentially analyzed to obtain the rate change of the instantaneous heat release rate.

[0047] When the rate change is positive, the adjustment direction of the current belt running speed is set to the speed increase direction; when the rate change is negative, the adjustment direction of the current belt running speed is set to the speed decrease direction, thus obtaining the belt speed adjustment direction.

[0048] Based on the absolute magnitude of the rate change, calculate the speed adjustment magnitude of the current belt running speed;

[0049] When the speed adjustment direction is the acceleration direction, the current belt running speed is summed with the speed adjustment amplitude. When the speed adjustment direction is the deceleration direction, the current belt running speed is subtracted from the speed adjustment amplitude to obtain the belt speed execution value.

[0050] In a preferred embodiment, calculating the speed adjustment amplitude of the current belt running speed based on the absolute amplitude of the rate change includes:

[0051] Retrieve the rate change at the previous moment before the rate change;

[0052] Based on the previous rate change, the speed adjustment amplitude is calculated, wherein the formula for calculating the speed adjustment amplitude is:

[0053] ;

[0054] In the formula, The speed adjustment amplitude, The preset speed conversion coefficient, The absolute magnitude of the rate change. It is the absolute value symbol. It is a natural exponential function. To preset the dimensionless damping coefficient, This refers to the previous rate change. This is a preset small constant.

[0055] In a preferred embodiment, the wide-belt alcoholysis is synergistically calibrated based on the alkaline solution addition temperature and the belt speed, with the alkaline solution temperature matching the initial activation conditions of alcoholysis and the belt speed matching the exothermic reaction and residence time as the core criteria, to obtain a polyvinyl alcohol product, including:

[0056] Based on the set alkali addition temperature, the polyvinyl acetate intermediate is uniformly mixed with the alkali solution heated at the set temperature to obtain a mixture.

[0057] Based on the belt speed, the mixture is subjected to alcoholysis on the belt to obtain polyvinyl alcohol product.

[0058] To address the above problems, the present invention also provides a flexible polyvinyl alcohol production system based on multi-reactor group collaborative control, the system comprising:

[0059] The first-stage polymerization reactor concentration deviation estimation module is used to collect the vinyl acetate and methanol content of the reflux liquid at the outlet of the first polymerization reactor in real time. Based on the feed composition ratio of the target polyvinyl alcohol variety, the module compares the actual composition of the reflux liquid with the feed composition to obtain the instantaneous deviation. Combining the feed flow rate, reflux liquid flow rate and the volume of material in the reactor, the module performs material balance and concentration conversion. After assigning the polarity of the deviation direction, the module estimates the dynamic deviation of the actual monomer concentration in the first polymerization reactor in real time.

[0060] The post-polymerization reactor residence time feedforward compensation module is used to perform reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor based on the dynamic deviation, to obtain the compensated residence time, and to determine the liquid level control threshold of the post-polymerization reactor based on the compensated residence time;

[0061] The alkali solution temperature matching and control module is used to introduce vinyl acetate monomer, methanol solvent and initiator into the first polymerization reactor and the second polymerization reactor. Based on the difference between the feed temperature of polyvinyl acetate intermediate and the reference temperature of alkali solution, the module performs reverse compensation adjustment on the alkali solution addition temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. According to the fluctuation of the feed temperature of polyvinyl acetate intermediate, the module performs temperature rise matching on the alkali solution addition temperature to obtain the execution value of the alkali solution addition temperature.

[0062] The alcoholysis heat release rate calculation module is used to calculate the instantaneous heat release rate of polyvinyl acetate intermediate during alcoholysis reaction based on the temperature difference of the belt temperature data in the wide belt alcoholysis machine.

[0063] The belt speed dynamic adjustment module is used to determine the belt speed adjustment direction and adjustment amplitude based on the instantaneous heat release rate and the change in the instantaneous heat release rate, and to introduce the rate change at the previous moment to dampen the adjustment amplitude, so as to perform exothermic response dynamic adjustment of the belt running speed of the wide belt alcoholysis machine and obtain the belt speed execution value.

[0064] The alcoholysis machine collaborative calibration output module is used to coordinate the wide belt alcoholysis based on the alkaline solution addition temperature and the belt speed, with the alkaline solution temperature matching the initial activation conditions of alcoholysis and the belt speed matching the reaction exothermic and residence time as the core basis, to obtain polyvinyl alcohol products.

[0065] Compared with the prior art, the present invention has the following beneficial effects:

[0066] 1. This invention estimates the dynamic deviation of monomer concentration in real time using reflux data from the first polymerization reactor, implements feedforward compensation for reflux disturbances in subsequent polymerization reactors based on residence time, and matches liquid level control thresholds to achieve dynamic coordinated control of multiple polymerization units. It can offset monomer concentration fluctuations within the reactor caused by reflux disturbances in real time, stabilize the degree of polymerization of polyvinyl acetate intermediates, adapt to flexible production conditions for multiple polyvinyl alcohol products, and ensure stable output of intermediate material quality in the polymerization process.

[0067] 2. This invention achieves temperature rise matching between the intermediate feed temperature and the alkali solution addition temperature. Combined with belt temperature measurement data, it calculates the instantaneous exothermic rate of alcoholysis and dynamically adjusts the belt speed of the wide-belt alcoholysis machine in an exothermic response manner, realizing the linkage control between alkali solution temperature and belt running speed. This precisely adapts to the real-time exothermic state of the alcoholysis reaction, suppresses deviations in reaction conditions during the alcoholysis process, stabilizes the degree of alcoholysis index of polyvinyl alcohol products, reduces quality abnormalities caused by process fluctuations, and effectively improves the overall production efficiency of polyvinyl alcohol. Attached Figure Description

[0068] Figure 1This is a schematic diagram of a flexible polyvinyl alcohol production method based on multi-reactor group collaborative control provided in an embodiment of the present invention.

[0069] Figure 2 A functional block diagram of a flexible polyvinyl alcohol production system based on multi-reactor group collaborative control provided in an embodiment of the present invention;

[0070] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0071] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0072] This application provides a flexible polyvinyl alcohol (PVA) production method based on multi-reactor group collaborative control. The execution entity of this flexible PVA production method includes, but is not limited to, at least one of the following electronic devices that can be configured to execute the method provided in this application: a server, a terminal, etc. In other words, the flexible PVA production method based on multi-reactor group collaborative control can be executed by software or hardware installed on a terminal device or a server device. The server includes, but is not limited to, a single server, a server cluster, a cloud server, or a cloud server cluster. The server can be an independent server or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks (CDNs), and big data and artificial intelligence platforms.

[0073] Reference Figure 1 The diagram shown is a schematic flow chart of a flexible polyvinyl alcohol (PVA) production method based on multi-reactor group collaborative control according to an embodiment of the present invention. In this embodiment, the flexible PVA production method based on multi-reactor group collaborative control includes:

[0074] S01. Real-time acquisition of vinyl acetate and methanol content in the reflux liquid at the outlet of the first polymerization reactor, and based on the feed composition ratio of the target polyvinyl alcohol variety, the instantaneous deviation is obtained by comparing the actual composition of the reflux liquid with the feed composition. Material balance and concentration conversion are performed by combining the feed flow rate, reflux liquid flow rate and material volume in the reactor. After assigning the polarity of the deviation direction, the dynamic deviation of the actual monomer concentration in the first polymerization reactor is estimated in real time.

[0075] In this embodiment of the invention, the vinyl acetate and methanol contents of the reflux liquid at the outlet of the first polymerization reactor are collected in real time. Based on the feed composition ratio of the target polyvinyl alcohol variety, the instantaneous deviation is obtained by comparing the actual composition of the reflux liquid with the feed composition. Material balance and concentration conversion are performed by combining the feed flow rate, reflux liquid flow rate, and material volume in the reactor. After assigning a polarity to the deviation direction, the dynamic deviation of the actual monomer concentration in the first polymerization reactor is estimated in real time, including:

[0076] Obtain the degree of polymerization and degree of alcoholysis index of the target polyvinyl alcohol variety, and based on the degree of polymerization index, determine the composition ratio of the first batch feed and the basic residence time of the subsequent batches.

[0077] Based on the stated degree of alcoholysis index, the reference temperature of the alkaline solution and the reference speed of the belt in the alcoholysis section are determined.

[0078] At the outlet of the reflux condenser in the first polymerization reactor, the vinyl acetate and methanol content of the reflux liquid were continuously and in real time collected.

[0079] The instantaneous deviation is obtained by comparing the actual composition ratio of the vinyl acetate content and the methanol content with the composition ratio of the first batch feed.

[0080] Based on the real-time monitoring values ​​of the feed flow rate and the reflux flow rate of the first polymerization reactor, the instantaneous deviation is converted into a material difference to obtain the change in the total amount of vinyl acetate monomer.

[0081] Based on the real-time monitoring value of the material volume in the first polymerization reactor, the change value of the total amount of vinyl acetate monomer is converted into concentration to obtain the actual deviation of the total amount of vinyl acetate monomer.

[0082] The concentration deviation direction of the instantaneous deviation is used as a positive or negative polarity indicator, and the actual deviation amplitude is assigned a positive or negative sign to obtain the dynamic deviation.

[0083] The pre-entered degree of polymerization (DOP) and degree of hydrolysis (DH) indices corresponding to the target polyvinyl alcohol (PVA) variety are retrieved. The DOP and DH indices are derived from the established technical specifications of the target PVA product to be produced. Based on the obtained DOP indices, the initial feed composition ratio and subsequent reactor residence time are retrieved from the stored process correspondence. The process correspondence is established through small-scale polymerization kinetic experiments at the target DOP combined with pilot-scale production line calibration. The typical range for the initial feed composition (based on vinyl acetate mass fraction) is 35%-55%, the corresponding methanol solvent mass fraction is 45%-65%, and the initiator accounts for 0.01%-0.1% of the vinyl acetate mass. The typical range for the subsequent reactor residence time is 2-6 hours, with the specific value increasing as the target DOP increases.

[0084] According to the acquired alcoholysis degree index, the reference temperature of the lye in the alcoholysis section and the reference speed of the belt are read from the stored process correspondence. The typical range of the reference temperature of the lye is 30℃-50℃, and the typical range of the reference speed of the belt is 0.5m / min-2.5m / min. Both are matched and calibrated according to the target alcoholysis degree requirement. The higher the alcoholysis degree requirement, the correspondingly higher the reference temperature of the lye, and the correspondingly lower the reference speed of the belt.

[0085] An on-line component collection device is installed at the position of the outlet pipeline of the reflux condenser supporting the first polymerizer. The on-line component collection device continuously extracts the reflux liquid material at the outlet position of the reflux condenser, uninterruptedly completes the capture of the material components of vinyl acetate content and methanol content inside the reflux liquid, and continuously obtains the vinyl acetate content and methanol content of the reflux liquid.

[0086] The collected vinyl acetate content and methanol content in the reflux liquid are converted to obtain the actual composition ratio of the reflux liquid, the actual composition ratio of the reflux liquid and the already read composition ratio of the first polymerizer feed are compared item by item for component check, and the difference result obtained between the two groups of composition ratios is taken as the instantaneous deviation.

[0087] The real-time monitoring value of the feed flow rate of the first polymerizer obtained by the flow collection device on the feed pipeline of the first polymerizer is read, and the real-time monitoring value of the reflux liquid flow rate obtained by the flow collection device on the reflux pipeline is read at the same time. The two sets of flow rate values are used to carry out a material difference conversion operation on the obtained instantaneous deviation. The material difference conversion operation is carried out according to the material balance method of subtracting the total amount of materials carried out by reflux from the total amount of materials entering the first polymerizer, which is specifically implemented in the following steps: first, four sets of data including the feed volume flow rate, the set concentration of vinyl acetate in the feed, the reflux liquid volume flow rate, and the measured concentration of vinyl acetate in the reflux liquid at the same moment are synchronously collected; then the amount of vinyl acetate monomer carried by the two streams per unit time is calculated respectively, the monomer amount at the feed end is obtained by multiplying the feed volume flow rate by the concentration of vinyl acetate in the feed, and the monomer amount at the reflux end is obtained by multiplying the reflux liquid volume flow rate by the measured concentration of vinyl acetate in the reflux liquid; finally, the monomer amount at the reflux end is subtracted from the monomer amount at the feed end, and the obtained result is the change value of the total amount of vinyl acetate monomer in the polymerizer per unit time. A positive value indicates that the total amount of monomer in the polymerizer increases, and a negative value indicates that the total amount of monomer in the polymerizer decreases. After the conversion is completed, the change value of the total amount of vinyl acetate monomer is obtained.

[0088] The real-time monitoring value of the material volume in the first polymerizer output by the liquid level detection device on the main body of the first polymerizer is read, and the real-time monitoring value of the material volume is used to carry out a concentration conversion operation on the obtained change value of the total amount of vinyl acetate monomer. The concentration conversion operation is completed by dividing the change value of the total monomer amount by the material volume in the polymerizer, and the actual deviation amplitude of the total amount of vinyl acetate monomer is obtained after the conversion.

[0089] Identify the direction of concentration deviation represented by the instantaneous deviation. The direction of concentration deviation is divided into the direction where the monomer concentration in the reactor is higher than the set ratio and the direction where the monomer concentration in the reactor is lower than the set ratio. The identified direction of concentration deviation is used as a positive or negative polarity indicator. The positive or negative polarity indicator is assigned to the actual deviation amplitude that has been obtained. The actual deviation amplitude with positive or negative signs is directly used as the dynamic deviation.

[0090] The beneficial effects include: by retrieving the degree of polymerization and degree of alcoholysis indices corresponding to the established technical specifications of the target polyvinyl alcohol product, and reading the matching process parameters, the process parameters can be made to perfectly match the actual production requirements of the product to be produced. By continuously acquiring the vinyl acetate and methanol content of the reflux liquid using online component acquisition devices, the true compositional state of the reflux material can be continuously monitored. Flow rate and material volume data are acquired using various acquisition devices configured in the pipelines and reactors, and material difference and concentration conversions are performed according to the material balance method. Dynamic deviation is generated by combining the instantaneous deviation amount with the concentration deviation direction. This can completely capture the changes in monomer concentration within the reactor caused by reflux disturbances, directly reflecting the true deviation state of monomer concentration inside the first polymerization reactor. This provides a reliable input basis for subsequent polymerization reactors to carry out reflux disturbance feedforward compensation, avoiding inaccurate subsequent process adjustments caused by the inability to accurately grasp the actual state of monomers within the reactor, and ensuring the reliability of the basic data source for multi-reactor group coordinated control.

[0091] S02. Based on the dynamic deviation, perform reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor to obtain the compensated residence time. Based on the compensated residence time, determine the liquid level control threshold of the post-polymerization reactor.

[0092] In this embodiment of the invention, the step of performing reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor based on the dynamic deviation to obtain the compensated residence time includes:

[0093] The deviation magnitude of the dynamic deviation is quantified and extracted to obtain the deviation value of the dynamic deviation;

[0094] When the deviation polarity of the dynamic deviation indicates that the monomer concentration in the first polymerization reactor is lower than the target value, the direction of adjusting the residence time in the subsequent polymerization reactor is determined as the extension direction.

[0095] When the deviation from polarity indicates that the monomer concentration in the first polymerization reactor is higher than the target value, the direction of adjusting the residence time in the subsequent polymerization reactor is determined to be the shortening direction.

[0096] The product of the deviation value and the residence time of the post-reactor foundation is used as the compensation increment;

[0097] The residence time of the post-reactor base is accumulated with the compensation increment over time to obtain the residence time after compensation.

[0098] The step of determining the liquid level control threshold of the post-polymerization reactor based on the compensated residence time includes:

[0099] The initial liquid level control threshold and the basic residence time of the post-polymerization reactor are retrieved.

[0100] The compensated dwell time is compared with the basic dwell time to obtain the dwell time deviation ratio.

[0101] When the duration deviation ratio indicates that the compensated dwell time is greater than the basic dwell time, the initial liquid level control threshold is adjusted upward.

[0102] When the duration deviation ratio indicates that the compensated residence time is less than the basic residence time, the initial liquid level control threshold is adjusted downward to obtain the liquid level control threshold of the post-polymerization reactor.

[0103] The obtained dynamic deviation is subjected to a quantitative extraction operation to determine the magnitude of the deviation. The numerical value corresponding to the magnitude of the dynamic deviation is read and directly used as the deviation amount. The deviation amount is the relative deviation rate of the monomer concentration relative to the target value, and the value range is -15% to +15% under normal production conditions.

[0104] The deviation polarity carried by the dynamic deviation is identified. The deviation polarity comes from the positive or negative sign given in the dynamic deviation generation stage. The identification results show that when the monomer concentration in the first polymerization reactor is lower than the target value, the direction of adjusting the residence time in the subsequent polymerization reactor is defined as the extension direction.

[0105] The deviation polarity carried by the dynamic deviation is identified. The deviation polarity comes from the positive or negative sign given in the dynamic deviation generation stage. The identification results show that when the monomer concentration in the first polymerization reactor is higher than the target value, the direction of adjusting the residence time in the subsequent polymerization reactor is defined as the shortening direction.

[0106] Read the obtained deviation value, read the initial residence time of the reactor obtained based on the target degree of polymerization index of polyvinyl alcohol, multiply the value corresponding to the deviation value and the duration value corresponding to the initial residence time of the reactor, and use the time value produced after multiplication as the compensation increment.

[0107] The system reads the initial residence time in the reactor obtained from the target degree of polymerization index of polyvinyl alcohol, reads the compensation increment, adds the time value corresponding to the initial residence time in the reactor to the time value corresponding to the compensation increment, and uses the time result after the addition process as the compensated residence time.

[0108] The initial liquid level control threshold of the post-polymerization reactor is retrieved. The initial liquid level control threshold is preset according to the process specification corresponding to the target polyvinyl alcohol variety. The initial liquid level control threshold is calculated as a percentage of the effective volume of the post-polymerization reactor, with a typical range of 60%-85%. The setting principle is to ensure that the material reaches the reaction depth requirement when the basic residence time in the reactor is reached. The basic residence time of the post-polymerization reactor obtained in the early stage based on the degree of polymerization index of the target polyvinyl alcohol is retrieved.

[0109] Read the time value corresponding to the compensated dwell time that has been obtained, and read the time value corresponding to the retrieved basic dwell time of the reactor. Compare the two sets of time values, and divide the difference between the compensated dwell time and the basic dwell time of the reactor by the basic dwell time of the reactor to obtain the time deviation ratio.

[0110] Read the obtained duration deviation ratio. If the result corresponding to the duration deviation ratio shows that the compensated dwell time is greater than the basic dwell time, perform an upward adjustment operation on the initial liquid level control threshold. The upward adjustment changes the limit position of liquid level control according to the proportion corresponding to the duration deviation ratio.

[0111] Read the obtained duration deviation ratio. If the result corresponding to the duration deviation ratio shows that the compensated residence time is less than the basic residence time, perform a downward adjustment operation on the initial liquid level control threshold. The downward adjustment changes the liquid level control boundary position according to the proportion corresponding to the duration deviation ratio. The liquid level control boundary produced after the adjustment is completed is used as the liquid level control threshold of the post-polymerization reactor.

[0112] The beneficial effect is that the compensation increment is determined by the deviation value obtained from dynamic deviation extraction, and the post-compensation residence time is generated by combining the corresponding adjustment direction. This allows for feedforward compensation of the backflow disturbance generated in the first polymerization reactor. The residence time of the material in the subsequent polymerization reactor is changed according to the actual change of monomer concentration in the reactor, offsetting the impact of monomer concentration fluctuations in the first polymerization reactor on subsequent processes. Furthermore, the residence time deviation ratio is obtained by comparing the post-compensation residence time with the basic residence time in the subsequent reactor. The initial liquid level control threshold is adjusted accordingly based on this ratio to obtain the liquid level control threshold for the subsequent polymerization reactor. This allows for synchronous matching of the material storage limit corresponding to the change in the residence time of the material in the subsequent polymerization reactor, maintaining a match between the actual residence state of the material in the reactor and the post-compensation residence time. This ensures the stability of the polymerization reaction inside the subsequent polymerization reactor, producing stable polyvinyl acetate intermediates, providing a qualified material basis for subsequent polyvinyl alcohol production processes.

[0113] S03. After introducing vinyl acetate monomer, methanol solvent and initiator into the first polymerization reactor and the second polymerization reactor, the alkali addition temperature is adjusted in reverse compensation based on the difference between the polyvinyl acetate intermediate feed temperature and the alkali solution reference temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. The alkali addition temperature is matched according to the fluctuation of the polyvinyl acetate intermediate feed temperature to obtain the alkali addition temperature execution value.

[0114] In this embodiment of the invention, after the vinyl acetate monomer, methanol solvent, and initiator are introduced into the first polymerization reactor and the second polymerization reactor, the alkali addition temperature is adjusted in reverse compensation based on the difference between the polyvinyl acetate intermediate feed temperature and the alkali solution reference temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. The alkali addition temperature is matched to the temperature rise based on the fluctuation of the polyvinyl acetate intermediate feed temperature to obtain the executed value of the alkali addition temperature, including:

[0115] Based on the aforementioned first batch feed composition ratio, vinyl acetate monomer, methanol solvent and initiator are introduced into the first polymerization reactor, and the first batch of polyvinyl acetate intermediate is obtained at the discharge port of the first polymerization reactor;

[0116] Based on the liquid level control threshold, the first batch of polyvinyl acetate intermediate is introduced into the subsequent polymerization reactor, and the polyvinyl acetate intermediate is obtained at the outlet of the subsequent polymerization reactor.

[0117] The feed temperature of the polyvinyl acetate intermediate is sensed in real time to obtain the feed temperature value of the polyvinyl acetate intermediate;

[0118] Retrieve the reference temperature value of the alkaline solution corresponding to the target polyvinyl alcohol variety;

[0119] The feed temperature reading is compared with the alkali reference temperature value in real time to obtain the temperature deviation of the feed temperature reading relative to the alkali reference temperature value.

[0120] When the temperature deviation indicates that the feed temperature is higher than the alkali reference temperature, the current addition temperature of the alkali is adjusted downward; when the temperature deviation indicates that the feed temperature is lower than the alkali reference temperature, the current addition temperature of the alkali is adjusted upward, thus obtaining the adjusted temperature value of the alkali.

[0121] The magnitude of the temperature deviation is used as the basis for correcting the adjusted temperature value. The larger the magnitude, the greater the correction to the adjusted temperature value, thus obtaining the execution value for the addition temperature of the alkali solution.

[0122] Based on the previously obtained composition ratio of the first batch feed, the material conveying devices on the vinyl acetate monomer conveying pipeline, the methanol solvent conveying pipeline, and the initiator conveying pipeline are turned on respectively to transport the vinyl acetate monomer, methanol solvent, and initiator into the first polymerization reactor. After the material completes the polymerization reaction inside the first polymerization reactor, the material is discharged out from the discharge port of the first polymerization reactor. The discharged reaction material is collected from the discharge port of the first polymerization reactor and the collected material is used as the first batch of polyvinyl acetate intermediate.

[0123] The temperature rise matching is based on the deviation between the actual feed temperature of the polyvinyl acetate intermediate and the reference temperature of the alkali solution. By adjusting the alkali solution temperature in the opposite direction, the fluctuation of the feed temperature of the intermediate is offset, ensuring that the starting temperature of the alcoholysis reaction is stable within the target range.

[0124] The feed path of the post-polymerization reactor is controlled according to the liquid level control threshold obtained. The intermediate of polyvinyl acetate from the first reactor is continuously fed into the interior of the post-polymerization reactor. The material continues to carry out the polymerization reaction inside the post-polymerization reactor. After the material completes the reaction, it is discharged from the outlet of the post-polymerization reactor. The discharged material is collected from the outlet of the post-polymerization reactor and is used as the polyvinyl acetate intermediate.

[0125] Temperature sensing devices are installed on the pipeline leading from the polyvinyl acetate intermediate to the alcoholysis section. The temperature sensing devices are in direct contact with the polyvinyl acetate intermediate flowing inside the pipeline and continuously capture the material temperature of the polyvinyl acetate intermediate. The temperature readings output by the temperature sensing devices are used as the feed temperature values ​​of the polyvinyl acetate intermediate.

[0126] The reference temperature value of the alkali solution corresponding to the target polyvinyl alcohol variety is retrieved. The reference temperature value of the alkali solution is preset and stored in advance according to the established production process specifications of the target polyvinyl alcohol variety. The reference temperature value of the alkali solution is retrieved from the stored process correspondence.

[0127] The feed temperature reading output by the temperature sensing device is compared with the retrieved alkali reference temperature value. The comparison operation reads the actual readings corresponding to the two sets of temperatures and calculates the difference between the two sets of temperature readings. This difference reflects the deviation of the feed temperature reading relative to the alkali reference temperature value, and this difference is used as the temperature deviation.

[0128] The system identifies the reading corresponding to the temperature deviation. When the reading indicates that the feed temperature is higher than the alkali reference temperature, the system controls the alkali heating device to reduce the heating output of the alkali, thereby adjusting the current alkali temperature downwards. When the reading indicates that the feed temperature is lower than the alkali reference temperature, the system controls the alkali heating device to increase the heating output of the alkali, thereby adjusting the current alkali temperature upwards. The temperature result produced after the adjustment operation is completed is taken as the adjusted temperature value of the alkali.

[0129] The deviation amplitude corresponding to the obtained temperature deviation is read. The deviation amplitude is taken from the reading difference corresponding to the temperature deviation. The adjusted temperature value of the alkali solution is further corrected according to the actual difference of the deviation amplitude. The correction adopts a proportional adjustment method, and the typical value of the proportional coefficient is 0.8-1.2. The larger the difference value corresponding to the deviation amplitude, the higher the degree of temperature change to the adjusted temperature value of the alkali solution is set. The temperature result produced after the correction process is completed is used as the execution value of the alkali solution addition temperature.

[0130] The beneficial effects are as follows: Firstly, the corresponding materials are fed into the first polymerization reactor according to the initial feed composition ratio to obtain the first batch of polyvinyl acetate intermediates. Then, relying on the liquid level control threshold, the materials are fed into subsequent polymerization reactors to produce polyvinyl acetate intermediates. This ensures that the materials produced in the polymerization process meet the polymerization reaction requirements of the corresponding product. Temperature sensors installed in the pipeline acquire the feed temperature of the polyvinyl acetate intermediates. This value is compared with the alkali solution reference temperature to obtain the temperature deviation. Based on the temperature deviation, the alkali solution temperature is adjusted and subsequently corrected to obtain the alkali solution addition temperature execution value. This allows the actual alkali solution addition temperature to match the actual state of the intermediate feed temperature, eliminating the interference of intermediate material temperature fluctuations on the initial conditions of the alcoholysis reaction, maintaining the temperature compatibility between materials in the initial stage of the alcoholysis reaction, stabilizing the basic reaction conditions of the alcoholysis reaction, reducing alcoholysis reaction anomalies caused by temperature factors, and providing process assurance for the production of stable-quality polyvinyl alcohol.

[0131] S04. Based on the temperature difference of the belt temperature data in the wide belt alcoholysis machine, calculate in real time the instantaneous exothermic rate of the polyvinyl acetate intermediate during the alcoholysis reaction.

[0132] In this embodiment of the invention, the step of calculating the instantaneous exothermic rate of the polyvinyl acetate intermediate during the alcoholysis reaction based on the temperature difference value of the belt temperature data in the wide-belt alcoholysis machine includes:

[0133] The temperature difference between adjacent temperature measuring points of the wide belt alcoholysis machine is retrieved, as well as the fixed interval between adjacent temperature measuring points and the current belt running speed of the wide belt alcoholysis machine.

[0134] Based on the fixed interval distance and the current belt running speed, the speed-distance conversion of the polyvinyl acetate intermediate is performed to obtain the travel time of the polyvinyl acetate intermediate;

[0135] The fixed interval distance is timed and merged according to the current belt running speed to obtain the travel time of the polyvinyl acetate intermediate.

[0136] Using the travel time as a time allocation scale, the temperature difference is evenly distributed to each time unit covered by the travel time to obtain the instantaneous temperature rise rate of the polyvinyl acetate intermediate within a unit travel time.

[0137] By combining the mass of material passing through the belt per unit time with the specific heat capacity of the material at constant pressure, the instantaneous temperature rise rate is converted into the instantaneous exothermic rate of the alcoholysis reaction.

[0138] The temperature readings are collected from two adjacent temperature measuring devices on the wide-belt alcoholysis machine. The installation positions of the two temperature measuring devices are fixed in advance. The temperature readings output by the two temperature measuring devices are compared and the difference is taken as the temperature difference between adjacent temperature measuring points. The spatial distance between the installation positions of the two temperature measuring devices is read. This spatial distance is taken as the fixed interval distance between adjacent temperature measuring points. The typical range of the fixed interval distance is 0.5m-2m. The rotation status reading is collected and output by the speed measuring device of the belt rotation position. This rotation status reading is taken as the current belt running speed of the wide-belt alcoholysis machine.

[0139] Based on the obtained fixed interval distance and the obtained current belt speed, simulate the complete process of the polyvinyl acetate intermediate following the belt to complete the position movement, and calculate the time required for the intermediate to travel the fixed interval distance. The calculated time result is used as the travel time of the polyvinyl acetate intermediate.

[0140] Referring to the already acquired fixed interval distance and the already acquired current belt speed, the spatial distance measurement method is converted into a time measurement method. The conversion operation is carried out according to the time required for the material to follow the belt to move the fixed interval distance. Specifically, the following steps are performed: First, retrieve the fixed interval distance parameter between adjacent temperature measuring points that has been pre-entered into the system, and at the same time, read the real-time running speed fed back by the belt drive device; then divide the fixed interval distance by the current belt speed to calculate the time required for the polyvinyl acetate intermediate to move from the upstream temperature measuring point to the downstream temperature measuring point with the belt. This time is the travel time of the material in this section. The time result obtained after the conversion is used as the travel time of the polyvinyl acetate intermediate.

[0141] Using the travel time already obtained as a time allocation benchmark, the obtained temperature difference is divided and distributed to each time interval experienced in the process of traveling that distance. The division and distribution operation is processed equally in such a way that the temperature difference completely corresponds to the total travel time. After the equalization process is completed, the instantaneous temperature rise rate of the polyvinyl acetate intermediate in a unit travel time is obtained.

[0142] The system collects the material flow rate output from the weighing device at the conveyor belt outlet. This flow rate represents the mass of material passing through the belt per unit time, i.e., the material mass flow rate per unit time. Under normal production conditions, the typical range is 0.5 kg / s to 5 kg / s. The specific heat capacity at constant pressure is derived from the inherent thermophysical properties of the polyvinyl acetate intermediate material itself. It is an inherent thermophysical parameter of the material, pre-stored in the control system after being determined by previous laboratory component testing. The typical value range is 1.8-2.2 kJ / (kg・℃), and this property is determined according to the composition of the material. The system also uses the obtained instantaneous temperature rise rate, i.e., the temperature increase of the material per unit time, calculated by dividing the temperature difference between adjacent temperature measuring points by the material flow rate. The heat conversion is performed based on the calculated heat consumption time, combined with the mass of material passing through the conveyor belt per unit time and the specific heat capacity of the material at constant pressure. The specific steps are as follows: First, unify the units of the three parameters to ensure that the units of mass flow rate, specific heat capacity, and temperature rise rate are compatible. Second, multiply the mass flow rate of the material per unit time, the specific heat capacity of the material at constant pressure, and the instantaneous temperature rise rate sequentially to obtain the total heat absorbed by the material during the temperature rise per unit time. Third, based on the heat conservation principle that all the heat released by the alcoholysis reaction is used for the temperature rise of the material, directly use this total heat value as the instantaneous heat release rate of the alcoholysis reaction. After the conversion, the instantaneous heat release rate of the alcoholysis reaction is obtained.

[0143] The beneficial effect is that by using temperature and speed measuring devices configured in the wide-belt alcoholysis machine to obtain the fixed interval distance of the temperature difference and the current belt speed, the travel time of the polyvinyl acetate intermediate can be obtained by measuring the distance and speed. This time-amounted scale is used to distribute the temperature difference and obtain the instantaneous temperature rise rate. Combined with the material mass obtained by the material weighing device and the inherent thermophysical properties of the material, the instantaneous exothermic rate of the alcoholysis reaction can be obtained. The actual heat release state of the alcoholysis process can be captured based on the actual operating information collected on-site by the alcoholysis machine, without relying on pre-set reaction experience values ​​for judgment. It can follow the real-time reaction state of the material on the belt to obtain the exothermic situation, providing a real operating condition basis for the dynamic adjustment of the belt speed. This avoids the process control lag caused by the inability to detect the exothermic changes of the alcoholysis reaction in a timely manner, ensuring that the subsequent adjustment actions of the alcoholysis section are in line with the actual reaction state on site.

[0144] S05. Based on the instantaneous heat release rate, determine the belt speed adjustment direction and adjustment amplitude based on the change in the instantaneous heat release rate, and introduce the rate change at the previous moment to dampen the adjustment amplitude, and perform exothermic response dynamic adjustment on the belt running speed of the wide belt alcoholysis machine to obtain the belt speed execution value.

[0145] In this embodiment of the invention, the step of determining the belt speed adjustment direction and adjustment amplitude based on the instantaneous heat release rate and the change in the instantaneous heat release rate, and introducing the rate change at a previous moment to dampen the adjustment amplitude, and performing exothermic response dynamic adjustment of the belt running speed of the wide-belt alcoholysis machine to obtain the belt speed execution value, includes:

[0146] The instantaneous heat release rate is continuously differentially divided to obtain the rate change of the instantaneous heat release rate;

[0147] When the rate change is positive, the adjustment direction of the current belt running speed is set to the speed increase direction; when the rate change is negative, the adjustment direction of the current belt running speed is set to the speed decrease direction, thus obtaining the belt speed adjustment direction.

[0148] Based on the absolute magnitude of the rate change, calculate the speed adjustment magnitude of the current belt running speed;

[0149] When the speed adjustment direction is the acceleration direction, the current belt running speed is summed with the speed adjustment amplitude. When the speed adjustment direction is the deceleration direction, the current belt running speed is subtracted from the speed adjustment amplitude to obtain the belt speed execution value.

[0150] The calculation of the speed adjustment amplitude of the current belt running speed based on the absolute amplitude of the rate change includes:

[0151] Retrieve the rate change at the previous moment before the rate change;

[0152] Based on the previous rate change, the speed adjustment amplitude is calculated, wherein the formula for calculating the speed adjustment amplitude is:

[0153] ;

[0154] In the formula, The speed adjustment amplitude, The preset speed conversion coefficient, The absolute magnitude of the rate change. It is the absolute value symbol. It is a natural exponential function. To preset the dimensionless damping coefficient, This refers to the previous rate change. This is a preset small constant.

[0155] The instantaneous exothermic rates of the alcoholysis reaction obtained at two consecutive time points are read. The difference between the instantaneous exothermic rate at the later time point and the instantaneous exothermic rate at the earlier time point is compared. The difference obtained after comparing the instantaneous exothermic rates at the two time points is taken as the rate change of the instantaneous exothermic rate.

[0156] Identify the readings corresponding to the obtained rate changes. If the readings show a positive value, define the adjustment direction corresponding to the current belt speed as the acceleration direction. If the readings show a negative value, define the adjustment direction corresponding to the current belt speed as the deceleration direction. After defining the direction, the belt speed adjustment direction is obtained.

[0157] The positive and negative indicators of the stripping rate change reading only retain the actual degree of deviation corresponding to the reading. This degree of deviation is used as the absolute amplitude of the rate change, and the speed adjustment amplitude corresponding to the current belt running speed is determined based on this absolute amplitude.

[0158] The system identifies the speed adjustment direction of the belt. If the identification result shows that the speed adjustment direction is an acceleration direction, the system adds the speed change corresponding to the speed adjustment amplitude to the current belt running speed. If the identification result shows that the speed adjustment direction is a deceleration direction, the system subtracts the speed change corresponding to the speed adjustment amplitude from the current belt running speed. The resulting belt movement speed after the corresponding changes is used as the belt speed execution value.

[0159] Retrieve the rate change amount retained during the previous process execution. This retained rate change amount is used as the previous rate change amount at the previous moment. The previous rate change amount comes from the output result obtained after differential processing of the instantaneous heat release rate in the previous round.

[0160] By comparing the deviation between the previous rate change and the rate change obtained in the current cycle, the degree of change in the speed adjustment amplitude is constrained by referring to the deviation between the two sets of changes. The constraint process changes the actual change in the speed adjustment amplitude according to the deviation between the two sets of changes, and the corresponding speed adjustment amplitude is generated after the constraint process is completed.

[0161] The preset speed conversion coefficient was determined through multiple on-site commissioning tests based on actual polyvinyl alcohol production conditions. The reasonable belt speed adjustment corresponding to different degrees of heat release was recorded and compiled. After completing multiple sets of tests, the corresponding value of this coefficient was fixed. Its physical meaning is the belt speed adjustment corresponding to a unit change in heat release rate, with units of (m / s) / (J / s). A typical value range is 1×10⁻⁶. -6 -5×10 -5(m / s) / (J / s); The specific determination method is as follows: Under stable production conditions, the alcoholysis exothermic rate is gradually changed, and the belt speed adjustment amount that keeps the product alcoholysis degree within the qualified range is recorded. The proportional coefficient between the two is obtained through linear fitting, which is the preset speed conversion coefficient. The preset dimensionless damping coefficient is determined by on-site debugging tests based on the allowable drastic change of belt speed in the production process. The value of this coefficient is fixed by combining the allowable smoothness of the adjustment action in production. The physical meaning is the damping weight of the difference between the two exothermic changes on the adjustment amplitude. The typical value range is 0.2-1.0. When the production requires a smooth adjustment process and avoids speed oscillation, a larger value is taken; when a fast adjustment response is required, a smaller value is taken. The preset small constant is determined by process debugging tests to avoid the case of zeroing in the denominator calculation process. The value of this constant is fixed after verification under multiple sets of working conditions. The absolute amplitude of the rate change is taken from the offset obtained by comparing the difference between the instantaneous exothermic rate and stripping the positive and negative labels. The previous rate change was obtained by comparing the instantaneous heat release rate difference retained from the previous process.

[0162] This set of parameters works together to produce the speed adjustment amplitude, converting the change in the exothermic state of the alcoholysis section into the required adjustment range of the belt speed. At the same time, the exothermic change state of the previous process is introduced to constrain the adjustment range of this process, so that the belt speed adjustment range can be adapted to the changes in the exothermic state. The fluctuation information of the exothermic state is completely converted into an executable change in belt speed.

[0163] When the current heat release state changes in the same direction as the previous heat release state, the restraint effect weakens, and the output speed adjustment amplitude corresponds to the corresponding magnitude of belt speed change. When the current heat release state changes in the opposite direction to the previous heat release state, the restraint effect strengthens, and the output speed adjustment amplitude corresponds to the corresponding magnitude of belt speed change. This is to control the degree of belt speed change and avoid excessive changes in a single adjustment action.

[0164] The beneficial effect is that by comparing the instantaneous exothermic rates at different times, the rate change is obtained. The direction of belt speed adjustment is determined based on the rate change reading. Then, combined with the absolute amplitude of the rate change, and simultaneously retrieving the previous rate change, the speed adjustment amplitude is constrained. The belt speed is then adjusted accordingly based on the speed adjustment direction to obtain the belt speed execution value. This allows for exothermic response adjustment of the belt speed in real time, following the changes in the exothermic state of the alcoholysis reaction. By constraining the degree of adjustment based on the previous rate change, unreasonable changes in belt speed are avoided. This ensures that the material conveying rhythm of the belt matches the actual evolution of the alcoholysis exothermic reaction, thereby controlling the residence time of polyvinyl acetate intermediates in the alcoholysis section, suppressing process fluctuations caused by abnormal exothermic reactions, maintaining suitable reaction conditions, and ensuring the stability of the degree of alcoholysis index of the polyvinyl alcohol product.

[0165] S06. Based on the alkaline solution addition temperature and the belt speed, and taking the alkaline solution temperature matching the initial activation conditions of alcoholysis and the belt speed matching the reaction exothermic and residence time as the core basis, the wide belt alcoholysis is coordinated and adjusted to obtain polyvinyl alcohol product.

[0166] In this embodiment of the invention, based on the executed values ​​of the alkali addition temperature and the belt speed, and with the alkali temperature matching the initial activation conditions of alcoholysis and the belt speed matching the reaction exothermic reaction and residence time as the core criteria, the wide-belt alcoholysis is synergistically adjusted to obtain a polyvinyl alcohol product, including:

[0167] Based on the set alkali addition temperature, the polyvinyl acetate intermediate is uniformly mixed with the alkali solution heated at the set temperature to obtain a mixture.

[0168] Based on the belt speed, the mixture is subjected to alcoholysis on the belt to obtain polyvinyl alcohol product.

[0169] The alkali solution is heated according to the set alkali addition temperature. The alkali solution flows through the internal cavity of the heating device to receive heat. When the alkali solution flows out of the heating device, it reaches the temperature corresponding to the set alkali addition temperature. The alkali solution heated to the set temperature is then transported to the material mixing position. At the same time, the polyvinyl acetate intermediate is also transported to the same material mixing position. The two materials are continuously stirred inside the material mixing position to allow the polyvinyl acetate intermediate and the alkali solution heated to the set temperature to fully mix with each other. The material produced after the mixing operation is completed is called the mixed material.

[0170] The specific basis for the coordinated adjustment is as follows: the alkaline temperature matches the initial activation energy conditions of the alcoholysis reaction to ensure a stable initial reaction rate; the belt speed matches the instantaneous exothermic intensity and target residence time of the alcoholysis reaction to ensure that the reaction process is controllable.

[0171] The obtained belt speed execution value is transmitted to the belt drive mechanism of the wide belt alcoholysis machine. After receiving the instruction, the belt drive mechanism drives the belt to move continuously at the speed corresponding to the belt speed execution value. The produced mixture is continuously laid on the surface of the running belt. The mixture moves forward synchronously with the belt. During the movement of the belt, the mixture continues to undergo alcoholysis conversion reaction. After the material completes the alcoholysis conversion, it is discharged from the end of the belt. The material discharged from the end of the belt is the polyvinyl alcohol product.

[0172] The beneficial effects are as follows: The alkali solution is heated according to the set temperature for addition. The heated alkali solution and polyvinyl acetate intermediate are then transported to the mixing area for agitation and blending to obtain a mixture. This allows the two materials participating in the alcoholysis reaction to contact and mix under matched temperature conditions, eliminating the deviation in reaction initiation conditions caused by temperature mismatch. Furthermore, a belt drive mechanism drives the belt according to the set speed, spreading the mixture on the belt surface to complete the alcoholysis conversion and obtain polyvinyl alcohol (PVA) product. This allows the mixture to maintain an appropriate reaction residence time on the belt, achieving coordinated adjustment of alkali solution temperature and belt conveyor rhythm, ensuring the complete and orderly progress of the alcoholysis reaction, stabilizing the quality of the PVA product, and completing the closed-loop control of the entire process chain.

[0173] The target product was selected as polyvinyl alcohol 1799, with a nominal degree of polymerization of 1700 and an allowable fluctuation range of ±50, and a nominal degree of hydrolysis of 99.0% and an allowable fluctuation range of ±0.5%. The multi-reactor group collaborative control method of the present invention was used as an example, and the traditional fixed parameter production method was used as a comparative example. A continuous 72-hour stable production test was conducted. During the test, intermediate quality data, finished product quality data, production capacity operation data, and working condition recovery data after reflux disturbance were collected simultaneously in the production process. The core production and quality indicators were comprehensively compared and verified.

[0174] In terms of product quality stability, when using the multi-reactor group collaborative control method of this invention, the actual fluctuation range of the degree of polymerization of polyvinyl acetate intermediate is 1682-1721, with a relative fluctuation range of ±1.14%, while the fluctuation range of the degree of polymerization under the traditional fixed parameter production method is 1635-1768, with a relative fluctuation range of ±3.91%. Regarding the degree of alcoholysis of the finished polyvinyl alcohol, the actual fluctuation range of the degree of alcoholysis under the method of this invention is 98.82%-99.15%, with a relative fluctuation range of ±0.17%, while the fluctuation range of the degree of alcoholysis under the traditional method is 98.35%-99.52%, with a relative fluctuation range of ±0.59%. In terms of the final product qualification rate, the method of this invention can reach 99.2%, far exceeding the 82.7% of the traditional method, significantly improving product quality consistency.

[0175] In terms of production efficiency and resistance to disturbances, the average hourly capacity of a single line using the method of this invention can reach 1.38 t / h, which is significantly improved compared to 1.15 t / h of the traditional method. Under the condition of backflow disturbance, the production system of the method of this invention can be stably restored in no more than 12 minutes, while the traditional method requires at least 45 minutes to restore a stable production state. The advantages of production fault tolerance and dynamic response capability are obvious.

[0176] Based on the above quantitative comparison data, it can be seen that after adopting the multi-reactor group collaborative control scheme of the present invention, the degree of polymerization fluctuation of polyvinyl acetate intermediate is reduced by 70.8%, the degree of alcoholysis fluctuation of polyvinyl alcohol product is reduced by 71.2%, the product qualification rate is increased by 16.5 percentage points, the single-line capacity is increased by 20%, and the production stabilization recovery time after reflux disturbance is shortened by more than 73%, which can significantly improve the stability and overall operating efficiency of flexible production of multiple varieties.

[0177] like Figure 2 The diagram shown is a functional block diagram of a flexible polyvinyl alcohol production system based on multi-reactor group collaborative control provided in an embodiment of the present invention.

[0178] The polyvinyl alcohol flexible production system 10 based on multi-reactor group collaborative control described in this invention can be installed in an electronic device. Depending on the functions implemented, the polyvinyl alcohol flexible production system 10 based on multi-reactor group collaborative control may include a first-reactor concentration deviation estimation module 11, a subsequent-reactor dwell time feedforward compensation module 12, an alkali solution temperature matching and control module 13, an alcohol deheating rate calculation module 14, a belt speed dynamic adjustment module 15, and an alcoholysis machine collaborative calibration output module 16. The module described in this invention can also be called a unit, referring to a series of computer program segments that can be executed by an electronic device processor and perform a fixed function, stored in the electronic device's memory.

[0179] In this embodiment, the functions of each module / unit are as follows:

[0180] The first reactor concentration deviation estimation module 11 is used to collect the vinyl acetate content and methanol content of the reflux liquid at the outlet of the first polymerization reactor in real time, and based on the first reactor feed composition ratio of the target polyvinyl alcohol variety, compare the actual composition of the reflux liquid with the feed composition to obtain the instantaneous deviation. Combine the feed flow rate, reflux liquid flow rate and the material volume in the reactor to perform material balance and concentration conversion. After assigning the polarity of the deviation direction, the module estimates the dynamic deviation of the actual monomer concentration in the first polymerization reactor in real time.

[0181] The post-polymerization reactor residence time feedforward compensation module 12 is used to perform reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor based on the dynamic deviation, to obtain the compensated residence time, and to determine the liquid level control threshold of the post-polymerization reactor based on the compensated residence time.

[0182] The alkali solution temperature matching and control module 13 is used to introduce vinyl acetate monomer, methanol solvent and initiator into the first polymerization reactor and the second polymerization reactor, and to perform reverse compensation adjustment on the alkali solution addition temperature based on the difference between the polyvinyl acetate intermediate feed temperature and the alkali solution reference temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. According to the fluctuation of the polyvinyl acetate intermediate feed temperature, the alkali solution addition temperature is matched to obtain the alkali solution addition temperature execution value.

[0183] The alcoholysis heat release rate calculation module 14 is used to calculate the instantaneous heat release rate of polyvinyl acetate intermediate during alcoholysis reaction in real time based on the temperature difference of the belt temperature data in the wide belt alcoholysis machine.

[0184] The belt speed dynamic adjustment module 15 is used to determine the belt speed adjustment direction and adjustment amplitude based on the instantaneous heat release rate and the change in the instantaneous heat release rate, and to introduce the rate change in the preceding time to dampen the adjustment amplitude, so as to perform exothermic response dynamic adjustment of the belt running speed of the wide belt alcoholysis machine and obtain the belt speed execution value.

[0185] The alcoholysis machine co-calibration output module 16 is used to coordinate the wide belt alcoholysis based on the alkaline addition temperature and the belt speed, with the alkaline temperature matching the initial activation conditions of alcoholysis and the belt speed matching the reaction exothermic and residence time as the core basis, to obtain polyvinyl alcohol products.

[0186] In the several embodiments provided by this invention, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the system embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may be used in actual implementation.

[0187] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0188] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional modules.

[0189] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0190] This application embodiment can acquire and process relevant data based on artificial intelligence technology. Artificial intelligence is the theory, method, technology, and application system that uses digital computers or machines controlled by digital computers to simulate, extend, and expand human intelligence, perceive the environment, acquire knowledge, and use that knowledge to obtain optimal results.

[0191] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A flexible production method for polyvinyl alcohol based on multi-reactor group collaborative control, characterized in that, The method includes: S01. Real-time acquisition of vinyl acetate and methanol content in the reflux liquid at the outlet of the first polymerization reactor, and based on the feed composition ratio of the target polyvinyl alcohol variety, the instantaneous deviation is obtained by comparing the actual composition of the reflux liquid with the feed composition. Material balance and concentration conversion are performed by combining the feed flow rate, reflux liquid flow rate and material volume in the reactor. After assigning the polarity of the deviation direction, the dynamic deviation of the actual monomer concentration in the first polymerization reactor is estimated in real time. S02. Based on the dynamic deviation, perform reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor to obtain the compensated residence time. Based on the compensated residence time, determine the liquid level control threshold of the post-polymerization reactor. S03. After introducing vinyl acetate monomer, methanol solvent and initiator into the first polymerization reactor and the second polymerization reactor, the alkali addition temperature is adjusted in reverse compensation based on the difference between the polyvinyl acetate intermediate feed temperature and the alkali solution reference temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. The alkali addition temperature is matched according to the fluctuation of the polyvinyl acetate intermediate feed temperature to obtain the alkali addition temperature execution value. S04. Based on the temperature difference of the belt temperature data in the wide belt alcoholysis machine, calculate in real time the instantaneous exothermic rate of the polyvinyl acetate intermediate during the alcoholysis reaction. S05. Based on the instantaneous heat release rate, determine the belt speed adjustment direction and amplitude using the change in the instantaneous heat release rate as the basis, and introduce the rate change at previous moments to dampen the adjustment amplitude, thereby dynamically adjusting the belt running speed of the wide-belt alcoholysis machine in an exothermic response manner to obtain the belt speed execution value, including: The instantaneous heat release rate is continuously differentially analyzed to obtain the rate change of the instantaneous heat release rate. When the rate change is positive, the adjustment direction of the current belt running speed is set to the speed increase direction; when the rate change is negative, the adjustment direction of the current belt running speed is set to the speed decrease direction, thus obtaining the belt speed adjustment direction. Based on the absolute magnitude of the rate change, calculate the speed adjustment magnitude of the current belt running speed; When the speed adjustment direction is the speed increase direction, the current belt running speed is summed with the speed adjustment amplitude; when the speed adjustment direction is the speed decrease direction, the current belt running speed is subtracted from the speed adjustment amplitude to obtain the belt speed execution value. S06. Based on the alkaline solution addition temperature and the belt speed, the wide belt alcoholysis is coordinated and adjusted, with the alkaline solution temperature matching the initial activation conditions of alcoholysis and the belt speed matching the reaction exothermic and residence time as the core basis, to obtain polyvinyl alcohol products.

2. The flexible polyvinyl alcohol production method based on multi-reactor group collaborative control as described in claim 1, characterized in that, The method involves real-time acquisition of vinyl acetate and methanol content in the reflux liquid at the outlet of the first polymerization reactor. Based on the feed composition ratio of the target polyvinyl alcohol variety, the instantaneous deviation is obtained by comparing the actual composition of the reflux liquid with the feed composition. Material balance and concentration conversion are then performed using the feed flow rate, reflux liquid flow rate, and reactor volume. After assigning a polarity to the deviation direction, the dynamic deviation of the actual monomer concentration in the first polymerization reactor is estimated in real time, including: Obtain the degree of polymerization and degree of alcoholysis index of the target polyvinyl alcohol variety, and based on the degree of polymerization index, determine the composition ratio of the first batch feed and the basic residence time of the subsequent batches. Based on the stated degree of alcoholysis index, the reference temperature of the alkaline solution and the reference speed of the belt in the alcoholysis section are determined. At the outlet of the reflux condenser in the first polymerization reactor, the vinyl acetate and methanol content of the reflux liquid were continuously and in real time collected. The instantaneous deviation is obtained by comparing the actual composition ratio of the vinyl acetate content and the methanol content with the composition ratio of the first batch feed. Based on the real-time monitoring values ​​of the feed flow rate and the reflux flow rate of the first polymerization reactor, the instantaneous deviation is converted into a material difference to obtain the change in the total amount of vinyl acetate monomer. Based on the real-time monitoring value of the material volume in the first polymerization reactor, the change value of the total amount of vinyl acetate monomer is converted into concentration to obtain the actual deviation of the total amount of vinyl acetate monomer. The concentration deviation direction of the instantaneous deviation is used as a positive or negative polarity indicator, and the actual deviation amplitude is assigned a positive or negative sign to obtain the dynamic deviation.

3. The flexible polyvinyl alcohol production method based on multi-reactor group collaborative control as described in claim 2, characterized in that, The step of performing reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor based on the dynamic deviation to obtain the compensated residence time includes: The deviation magnitude of the dynamic deviation is quantified and extracted to obtain the deviation value of the dynamic deviation; When the deviation polarity of the dynamic deviation indicates that the monomer concentration in the first polymerization reactor is lower than the target value, the direction of adjusting the residence time in the subsequent polymerization reactor is determined as the extension direction. When the deviation from polarity indicates that the monomer concentration in the first polymerization reactor is higher than the target value, the direction of adjusting the residence time in the subsequent polymerization reactor is determined to be the shortening direction. The product of the deviation value and the residence time of the post-reactor foundation is used as the compensation increment; The residence time of the post-reactor base is accumulated with the compensation increment over time to obtain the residence time after compensation.

4. The flexible polyvinyl alcohol production method based on multi-reactor group collaborative control as described in claim 1, characterized in that, The step of determining the liquid level control threshold of the post-polymerization reactor based on the compensated residence time includes: The initial liquid level control threshold and the basic residence time of the post-polymerization reactor are retrieved. The compensated dwell time is compared with the basic dwell time to obtain the dwell time deviation ratio. When the duration deviation ratio indicates that the compensated dwell time is greater than the basic dwell time, the initial liquid level control threshold is adjusted upward. When the duration deviation ratio indicates that the compensated residence time is less than the basic residence time, the initial liquid level control threshold is adjusted downward to obtain the liquid level control threshold of the post-polymerization reactor.

5. The flexible polyvinyl alcohol production method based on multi-reactor group collaborative control as described in claim 1, characterized in that, After the vinyl acetate monomer, methanol solvent, and initiator are introduced into the first polymerization reactor and the second polymerization reactor, the alkali addition temperature is adjusted in reverse compensation based on the difference between the polyvinyl acetate intermediate feed temperature and the alkali solution reference temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. The alkali addition temperature is matched to the fluctuation of the polyvinyl acetate intermediate feed temperature to obtain the executed alkali addition temperature value, including: Based on the aforementioned first batch feed composition ratio, vinyl acetate monomer, methanol solvent and initiator are introduced into the first polymerization reactor, and the first batch of polyvinyl acetate intermediate is obtained at the discharge port of the first polymerization reactor; Based on the liquid level control threshold, the first batch of polyvinyl acetate intermediate is introduced into the subsequent polymerization reactor, and the polyvinyl acetate intermediate is obtained at the outlet of the subsequent polymerization reactor. The feed temperature of the polyvinyl acetate intermediate is sensed in real time to obtain the feed temperature value of the polyvinyl acetate intermediate; Retrieve the reference temperature value of the alkaline solution corresponding to the target polyvinyl alcohol variety; The feed temperature reading is compared with the alkali reference temperature value in real time to obtain the temperature deviation of the feed temperature reading relative to the alkali reference temperature value. When the temperature deviation indicates that the feed temperature is higher than the alkali reference temperature, the current addition temperature of the alkali is adjusted downward; when the temperature deviation indicates that the feed temperature is lower than the alkali reference temperature, the current addition temperature of the alkali is adjusted upward, thus obtaining the adjusted temperature value of the alkali. The magnitude of the temperature deviation is used as the basis for correcting the adjusted temperature value. The larger the magnitude, the greater the correction to the adjusted temperature value, thus obtaining the execution value for the addition temperature of the alkali solution.

6. The flexible polyvinyl alcohol production method based on multi-reactor group collaborative control as described in claim 1, characterized in that, The method of calculating the instantaneous exothermic rate of polyvinyl acetate intermediate during alcoholysis based on the temperature difference value of the belt temperature data in the wide-belt alcoholysis machine includes: The temperature difference between adjacent temperature measuring points of the wide belt alcoholysis machine is retrieved, as well as the fixed interval between adjacent temperature measuring points and the current belt running speed of the wide belt alcoholysis machine. Based on the fixed interval distance and the current belt running speed, the speed-distance conversion of the polyvinyl acetate intermediate is performed to obtain the travel time of the polyvinyl acetate intermediate; The fixed interval distance is timed and merged according to the current belt running speed to obtain the travel time of the polyvinyl acetate intermediate. Using the travel time as a time allocation scale, the temperature difference is evenly distributed to each time unit covered by the travel time to obtain the instantaneous temperature rise rate of the polyvinyl acetate intermediate within a unit travel time. By combining the mass of material passing through the belt per unit time with the specific heat capacity of the material at constant pressure, the instantaneous temperature rise rate is converted into the instantaneous exothermic rate of the alcoholysis reaction.

7. The flexible polyvinyl alcohol production method based on multi-reactor group collaborative control as described in claim 1, characterized in that, The calculation of the speed adjustment amplitude of the current belt running speed based on the absolute amplitude of the rate change includes: Retrieve the rate change at the previous moment before the rate change; Based on the previous rate change, the speed adjustment amplitude is calculated, wherein the formula for calculating the speed adjustment amplitude is: ； In the formula, The speed adjustment amplitude, The preset speed conversion coefficient, The absolute magnitude of the rate change. It is the absolute value symbol. It is a natural exponential function. To preset the dimensionless damping coefficient, This refers to the previous rate change. This is a preset small constant.

8. The flexible polyvinyl alcohol production method based on multi-reactor group collaborative control as described in claim 1, characterized in that, Based on the set values ​​of the alkali addition temperature and the belt speed, and with the alkali temperature matching the initial activation conditions of alcoholysis and the belt speed matching the exothermic reaction and residence time as the core criteria, the wide-belt alcoholysis is synergistically calibrated to obtain polyvinyl alcohol products, including: Based on the set alkali addition temperature, the polyvinyl acetate intermediate is uniformly mixed with the alkali solution heated at the set temperature to obtain a mixture. Based on the belt speed, the mixture is subjected to alcoholysis on the belt to obtain polyvinyl alcohol product.

9. A flexible polyvinyl alcohol production system based on multi-reactor group collaborative control, characterized in that, The system for implementing the flexible polyvinyl alcohol production method based on multi-reactor group collaborative control as described in claim 1 includes: The first-stage polymerization reactor concentration deviation estimation module is used to collect the vinyl acetate and methanol content of the reflux liquid at the outlet of the first polymerization reactor in real time. Based on the feed composition ratio of the target polyvinyl alcohol variety, the module compares the actual composition of the reflux liquid with the feed composition to obtain the instantaneous deviation. Combining the feed flow rate, reflux liquid flow rate and the volume of material in the reactor, the module performs material balance and concentration conversion. After assigning the polarity of the deviation direction, the module estimates the dynamic deviation of the actual monomer concentration in the first polymerization reactor in real time. The post-polymerization reactor residence time feedforward compensation module is used to perform reflux disturbance feedforward compensation on the basic residence time of the post-polymerization reactor based on the dynamic deviation, to obtain the compensated residence time, and to determine the liquid level control threshold of the post-polymerization reactor based on the compensated residence time; The alkali solution temperature matching and control module is used to introduce vinyl acetate monomer, methanol solvent and initiator into the first polymerization reactor and the second polymerization reactor. Based on the difference between the feed temperature of polyvinyl acetate intermediate and the reference temperature of alkali solution, the module performs reverse compensation adjustment on the alkali solution addition temperature. The adjustment amplitude is positively correlated with the temperature deviation amplitude. According to the fluctuation of the feed temperature of polyvinyl acetate intermediate, the module performs temperature rise matching on the alkali solution addition temperature to obtain the execution value of the alkali solution addition temperature. The alcoholysis heat release rate calculation module is used to calculate the instantaneous heat release rate of polyvinyl acetate intermediate during alcoholysis reaction based on the temperature difference of the belt temperature data in the wide belt alcoholysis machine. The belt speed dynamic adjustment module is used to determine the belt speed adjustment direction and amplitude based on the instantaneous heat release rate and the change in the instantaneous heat release rate, and to introduce the rate change at a previous moment to dampen the adjustment amplitude, thereby dynamically adjusting the belt running speed of the wide-belt alcoholysis machine in an exothermic response manner to obtain the belt speed execution value, including: The instantaneous heat release rate is continuously differentially analyzed to obtain the rate change of the instantaneous heat release rate. When the rate change is positive, the adjustment direction of the current belt running speed is set to the speed increase direction; when the rate change is negative, the adjustment direction of the current belt running speed is set to the speed decrease direction, thus obtaining the belt speed adjustment direction. Based on the absolute magnitude of the rate change, calculate the speed adjustment magnitude of the current belt running speed; When the speed adjustment direction is the speed increase direction, the current belt running speed is summed with the speed adjustment amplitude; when the speed adjustment direction is the speed decrease direction, the current belt running speed is subtracted from the speed adjustment amplitude to obtain the belt speed execution value. The alcoholysis machine collaborative calibration output module is used to coordinate the wide belt alcoholysis based on the alkaline solution addition temperature and the belt speed, with the alkaline solution temperature matching the initial activation conditions of alcoholysis and the belt speed matching the reaction exothermic and residence time as the core basis, to obtain polyvinyl alcohol products.

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